1. This invention relates to welding with wire products, more particularly with bendable wires of normally unmalleable alloys suited for uses such as weld filler metals.
2. The fabrication of wire of metal alloys which are readily forged or drawn is easily undertaken. However, a considerable number of alloys can be readily cast but their metallurgical structure is such that they cannot be formed into wires by conventional cold or hot working processes. It is with these types of alloys that the present invention is particularly useful. Among these alloys are high temperature cobalt and nickel base superalloys, including those used for structural and hardfacing applications. To accomplish most types of welding it is desired to have filler metals in rod or wire form, and it is within this applied context that the invention is described in detail.
Nonforgeable welding alloys can presently be made into suitable wires by either casting or powder metal processes. In the former, wires are typically formed by centrifugally casting small rods; the minimum diameters and the maximum length-to-diameter ratios are limited according to known factors relating to castability. Alternatively, the alloys can be converted into a powder, as by atomization, and then pressed or extruded into wires of the desired diameter; however, these processes can be costly and small diameters are difficult to obtain. In both the foregoing instances, the rod or wire will still have the unyielding character of the cast alloy. And the minimum diameters that are formable from most alloys using these techniques are greater than those often desired for welding small workpieces. The diameter of oversize wires can be reduced by centerless grinding, for example, but such an operation is costly and results in the loss of valuable welding wire alloy.
Generally, even with inefficiency, most cast alloys cannot readily be made into wires of less than 1 mm diameter, and when they are made at diameters near the minimum, they tend to be rather fragile and prone to breakage during handling, if dropped or bent. Because of these constraints, small diameter wires usually come in relatively short lengths of about 20-40 cm. Therefore, they are not suited for continuous fusion welding processes such as GMA (Gas Metal Arc), but must be used in hand-fed GTA (Gas Tungsten Arc) processes instead, with attendant inefficiency in production and weld wire consumption.
Thus, there is a need for an improved small diameter weld filler metal wire which has sufficient malleability to endure the moderate bending that is characteristically imposed by automatic welding wire feeders. The improved wire will not be prone to undue breakage during normal handling or welding operations.
In our U.S. Pat. No. 4,250,229 entitled "Interlayers With Amorphous Structure For Brazing And Diffusion Bonding" we describe metal foils wherein a portion of the interlayer has an amorphous structure which imparts ductility to normally brittle alloys which melt during brazing and bonding processes.